It is known in the art to prepare preprinted pressure sensitive adhesive backed labels which have a transparent protective face (see, for example, U.S. Pat. No. 4,068,028, issued Jan. 10, 1978). In making such labels it is common to use water based adhesives and more particularly water based acrylic emulsion adhesives. Such label and tag making adhesives are normally applied in a liquid state containing 40% or more water or other liquid vehicle. While this simplifies the application of the adhesive to the substrate the moisture must be subsequently removed to produce the final adhesive backed product.
For example, a pressure sensitive label containing from about 3-5% of moisture by weight depending on the operation such as wide web adhesive coating and laminating of label stock, usually intended for future conversions as sold through a paper merchant, is cured to approximately 3% moisture while normal label substrates may contain up to 5%. If the adhesive at the time of lamination contains 40% or more moisture by weight, that excess must be driven off in the production of the final adhesive backing When applying such emulsion adhesive containing 40% or more moisture either by free flow extrusion by Mayer Rod, a 36 Mayer Rod would apply about 8 mils of wet adhesive at about 56% solids and would cure out at about 0.0009-0.001 mils thickness dry at 120 feet per minute with three ten foot zoned ovens, starting heat 225.degree. F. and ending heat 425.degree. F. Such wet emulsion adhesive application or coating at even high speeds of 800-1000 feet per minute or faster would require even more time and heat for curing. Moreover they require a tremendous amount of energy to dry the vehicle which is between 50-60% water.
On the other hand, hot melt adhesives may be extruded at high speeds onto substrates and cured in a very short time. Such material, however, requires expensive equipment for application and the use of considerable energy to melt the hot melt pellets and apply them in proper consistency. Such operations are expensive and time consuming and may even involve referring the product to an outside organization to apply the adhesive and dry it to a level satisfactory for the making of the label. This invention overcomes these difficulties and provides an adhesive with low moisture content which may be extruded on to a substrate and used almost immediately.